This study addressed the issue of low reading proficiency in Kentucky's students with disabilities, potentially exacerbated by post-third-grade curriculum changes. This quasi-experimental ex post facto comparative study aims to determine differences in the grade four reading achievement gap in students with disabilities compared to students without disabilities in the state of Kentucky. A stratified random sample of approximately 200 grade four and grade eight students from Kentucky's public schools was collected. After IRB approval, the de-identified archival K-Prep reading data was gathered from the Kentucky Board of Education. The study found eighth grade reading scores improved from 2012 to 2016, but the achievement gap for students with disabilities persisted, with no improvement among students with disabilities. The study found a reading achievement gap for disabled students, questioning Common Core and Chall's framework, especially for decoding support post-3rd grade. The findings underscore the need for nuanced data collection and analysis in assessing reading scores across subgroups such as students with disabilities. It suggests a necessity to develop targeted strategies for students with disabilities, which are potentially overlooked in the CCSS framework. Recommendations include a policy mandate for the science of reading instruction professional development for educators, emphasizing disaggregated data use to differentiate instruction and personalize learning plans for SWD, customize CCSS, offer additional support for SWD during "learning to read," provide fluency assessments, and extend foundational skills instruction. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]